1. Field of the Invention
The present invention relates to a detecting device, in particular to an apparatus for detecting a foreign object in a bill passageway.
2. Description of Related Art
As people require high efficiency and convenience in modern life, many kinds of automatic trading machines are located at many public places, such as automatic ticket seller machine, automatic exchange machine and automatic teller machine. However, some of those automatic trading machines are not under well monitored in those public places. Therefore, a bill validator is often installed in those automatic trading machines to prevent counterfeit bill. And kinds of anti-stealing devices are installed in those automatic trading machines to prevent bill stealing.
One kind of bills stealing is performed by attaching a foreign object like a wire, a string or a tape onto a bill. After the bill is inserted into the automatic trading machine and passes through the reorganization and is recorded by the automatic trading machine, the bill is pulled out from the automatic trading machine by the wire. In order to prevent this kind of bill stealing, kinds of detecting device is installed in the automatic trading machine to detect the foreign object attached on the bill. Then the automatic trading machine can shut down the power by itself or can cut off the foreign object attached on the bill by corresponding device to prevent bill from pulling out.
Conventional foreign object detecting apparatus installed in the bill passageway of the automatic trading machine has a light emitting diode arranged at a side of the passageway to be a light source. The light emitting diode emits a light beam across the passageway after the bill passing through the passageway. And a light detector is utilized to receive the light beam passed through the passageway. If the light is once blocked by the foreign object, the light detector will sense the variation of light beam so as to discover the presence of the foreign object.
However, the conventional foreign object detecting apparatus has its natural limitation of resolution and the very thin wire is difficult to be discovered. Therefore, a foreign object detecting apparatus with better resolution needs to be invented to well prevent the happen of those bill stealing.